ADM1da — model overview
The mechanistic process model behind this repository is ADM1da
(Schlattmann 2011), an agricultural-biogas extension of the classical
Anaerobic Digestion Model No. 1 (Batstone et al. 2002), implemented in
PyADM1ODE.
State vector — 41 components
Indices as in pyadm1/core/adm1.py:
Dissolved (0–11)
| Idx |
Symbol |
Meaning |
Unit |
| 0 |
S_su |
Monosaccharides |
kg COD/m³ |
| 1 |
S_aa |
Amino acids |
kg COD/m³ |
| 2 |
S_fa |
Long-chain fatty acids |
kg COD/m³ |
| 3 |
S_va |
Valerate (total) |
kg COD/m³ |
| 4 |
S_bu |
Butyrate (total) |
kg COD/m³ |
| 5 |
S_pro |
Propionate (total) |
kg COD/m³ |
| 6 |
S_ac |
Acetate (total) |
kg COD/m³ |
| 7 |
S_h2 |
Dissolved hydrogen |
kg COD/m³ |
| 8 |
S_ch4 |
Dissolved methane |
kg COD/m³ |
| 9 |
S_co2 |
Inorganic carbon (S_IC) |
kmol C/m³ |
| 10 |
S_nh4 |
Inorganic nitrogen (S_IN) |
kmol N/m³ |
| 11 |
S_I |
Soluble inert |
kg COD/m³ |
Particulate sub-fractions (12–21)
| Idx |
Symbol |
Meaning |
| 12 |
X_PS_ch |
Slowly disintegrating carbohydrates |
| 13 |
X_PS_pr |
Slowly disintegrating proteins |
| 14 |
X_PS_li |
Slowly disintegrating lipids |
| 15 |
X_PF_ch |
Fast disintegrating carbohydrates |
| 16 |
X_PF_pr |
Fast disintegrating proteins |
| 17 |
X_PF_li |
Fast disintegrating lipids |
| 18 |
X_S_ch |
Hydrolysable carbohydrates |
| 19 |
X_S_pr |
Hydrolysable proteins |
| 20 |
X_S_li |
Hydrolysable lipids |
| 21 |
X_I |
Particulate inert |
Biomass (22–28)
| Idx |
Symbol |
Meaning |
| 22 |
X_su |
Sugar degraders |
| 23 |
X_aa |
Amino-acid degraders |
| 24 |
X_fa |
LCFA degraders |
| 25 |
X_c4 |
Valerate/butyrate degraders |
| 26 |
X_pro |
Propionate degraders |
| 27 |
X_ac |
Acetoclasts (methanogens) |
| 28 |
X_h2 |
Hydrogenotrophic methanogens |
Charge balance (29–36)
| Idx |
Symbol |
Meaning |
| 29 |
S_cation |
Cations |
| 30 |
S_anion |
Anions |
| 31 |
S_va_ion |
Valerate ion |
| 32 |
S_bu_ion |
Butyrate ion |
| 33 |
S_pro_ion |
Propionate ion |
| 34 |
S_ac_ion |
Acetate ion |
| 35 |
S_hco3_ion |
Bicarbonate |
| 36 |
S_nh3 |
Free ammonia |
Gas phase (37–40)
| Idx |
Symbol |
Meaning |
| 37 |
p_gas_h2 |
H₂ partial pressure (bar) |
| 38 |
p_gas_ch4 |
CH₄ partial pressure (bar) |
| 39 |
p_gas_co2 |
CO₂ partial pressure (bar) |
| 40 |
pTOTAL |
Total gas pressure (bar) |
Main extensions over standard ADM1
- Two-pool disintegration — X_xc is replaced by X_PS (slow, k=0.04 d⁻¹)
and X_PF (fast, k=0.4 d⁻¹), each split into ch/pr/li.
- Explicit hydrolysable pools X_S_ch/pr/li (indices 18–20).
- Temperature-corrected kinetics via Arrhenius-θ per organism group.
- Modified inhibition — quadratic/cubic pH inhibition, free-acid
inhibition (KIHPRO, KIHAC), acetate competition.
- Doubled decay rate k_dec_ac = 0.04 d⁻¹ (classic: 0.02).
Built-in derived observables
The ADM1 object in pyadm1 exposes ready-to-use observables that can be
plugged in as extractors in the ObservationModel:
| Method |
Returned |
Q_GAS(), Q_CH4(), Q_CO2() |
Gas volume flows |
P_GAS() |
Partial pressures |
pH_l() |
Computed pH |
VFA(), TAC() |
Weighted VFA sum, buffer capacity |
FOSTAC(), AcvsPro() |
Early-warning ratios |
Sources
- Schlattmann, M. (2011). Agricultural extension of ADM1.
- Batstone, D. J. et al. (2002). The IWA Anaerobic Digestion Model No 1.
Water Science and Technology 45(10):65–73.
- Weinrich, S. & Nelles, M. (2021). Systematic simplification of the ADM1.
Bioresource Technology 333:125124.